The effects of infection by Erysiphe pisi on some aspects of the carbohydrate biochemistry of Pisum sativum
The effects of infection by Erysiphe pisi on some aspects of the carbohydrate biochemistry of Pisum sativum
The effect of infection by the powdery mildew, Erysiphe pisi, on the sucrose catabolism and starch biochemistry of mature leaves of pea, Pisum sativum, was investigated. Two pea cultivars were used during the study, cv. onward and cv. argenteum, the latter is thought to be similar to cv. onward apart from having an easily detachable leaf epidermis, thus enabling the physical domains of mesophyll and epidermis of to be separated. The enzymes of sucrose catabolism in mature, healthy leaves were investigated. Activities of sucrose synthase and α-glucosidase were low, while those of acid and alkaline invertases were high. The acid and alkaline invertases of mature leaves of cv. onward and cv. argenteum were partially purified and biochemically well characterised prior to assessing the effects of infection on these enzymes. Invertases were assayed using a leaf homogenate method. This method was compared with a leaf disc method, which has been used in other studies similar to the present one, and it was found that alkaline invertase activity could not be detected using the leaf disc method. Infection caused a significant increase in activity of both acid and alkaline invertases when whole leaves of cv. onward were assayed. When the mesophyll of cv. argenteum was considered, only the activity of alkaline invertase was significantly increased. Due to methodological reasons, epidermal invertases could not be reliably measured. The results were discussed in relation to the mode of uptake of nutrients by the mildew, and it was proposed that host respiration may account for more of the increased invertase activity than has previously been acknowledged. Levels of reducing sugars and sucrose in leaves were not altered by infection. It was suggested that turnover rates of these sugars, as well as pool sizes, would provide a more informative measure of the metabolic role of these compounds. Infection caused a significant decrease in starch levels of whole leaves of cv. onward. Activity of α-glucan phosphorylase, which is thought to be responsible for the degradation of leaf starch, was not increased by infection. Similarly, leaf total phosphate levels were not altered by infection. However, activity of ADP-glucose pyrophosphorylase, the enzyme responsible for the regulation of synthesis of leaf starch, was generally decreased in infected plants, thus providing a possible explanation of the mechanism of reduced leaf starch levels in infected plants. Fructans were not detected in either healthy or infected pea leaves.
University of Southampton
1990
Storr, Trevor
(1990)
The effects of infection by Erysiphe pisi on some aspects of the carbohydrate biochemistry of Pisum sativum.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The effect of infection by the powdery mildew, Erysiphe pisi, on the sucrose catabolism and starch biochemistry of mature leaves of pea, Pisum sativum, was investigated. Two pea cultivars were used during the study, cv. onward and cv. argenteum, the latter is thought to be similar to cv. onward apart from having an easily detachable leaf epidermis, thus enabling the physical domains of mesophyll and epidermis of to be separated. The enzymes of sucrose catabolism in mature, healthy leaves were investigated. Activities of sucrose synthase and α-glucosidase were low, while those of acid and alkaline invertases were high. The acid and alkaline invertases of mature leaves of cv. onward and cv. argenteum were partially purified and biochemically well characterised prior to assessing the effects of infection on these enzymes. Invertases were assayed using a leaf homogenate method. This method was compared with a leaf disc method, which has been used in other studies similar to the present one, and it was found that alkaline invertase activity could not be detected using the leaf disc method. Infection caused a significant increase in activity of both acid and alkaline invertases when whole leaves of cv. onward were assayed. When the mesophyll of cv. argenteum was considered, only the activity of alkaline invertase was significantly increased. Due to methodological reasons, epidermal invertases could not be reliably measured. The results were discussed in relation to the mode of uptake of nutrients by the mildew, and it was proposed that host respiration may account for more of the increased invertase activity than has previously been acknowledged. Levels of reducing sugars and sucrose in leaves were not altered by infection. It was suggested that turnover rates of these sugars, as well as pool sizes, would provide a more informative measure of the metabolic role of these compounds. Infection caused a significant decrease in starch levels of whole leaves of cv. onward. Activity of α-glucan phosphorylase, which is thought to be responsible for the degradation of leaf starch, was not increased by infection. Similarly, leaf total phosphate levels were not altered by infection. However, activity of ADP-glucose pyrophosphorylase, the enzyme responsible for the regulation of synthesis of leaf starch, was generally decreased in infected plants, thus providing a possible explanation of the mechanism of reduced leaf starch levels in infected plants. Fructans were not detected in either healthy or infected pea leaves.
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Published date: 1990
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Local EPrints ID: 462040
URI: http://eprints.soton.ac.uk/id/eprint/462040
PURE UUID: 74f27d58-b250-4b2a-8aa9-701711a475a1
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Date deposited: 04 Jul 2022 19:00
Last modified: 04 Jul 2022 19:00
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Author:
Trevor Storr
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